Saw blade, a sawing machine and a system thereof

ABSTRACT

A saw blade for a sawing machine for cutting micro trenches for receiving at least one duct or cable. The saw blade includes coding elements such as holes, depressions or protrusions. The holes, depressions or protrusions form at least one code symbol representing a unique identity (ID) for the saw blade.

TECHNICAL FIELD

The present invention relates to a saw blade for a sawing machine, asawing machine and a system thereof. More specifically the inventionrelates to a saw blade, a sawing machine and a system according to thepreambles of the independent claims.

BACKGROUND OF THE INVENTION

The expansion of fibre optic networks for communication in residentialareas is often hampered by the high cost of excavation and restorationof the road layer, such as asphalt or concrete. A typical residentialconnection may cost approximately EUR 3 000 plus VAT, and hence manyhomeowners are reluctant to make such an investment. This in turn meansthat the connection rate for houses is low when a residential area isbuilt, which further increases the cost of connecting. The reason forthis is that the cost for the backbone is more or less independent ofthe connection rate, and a low connection rate means that fewer houseswill have to bear the total cost for the backbone.

An alternative, to provide house connections through green open spacesat the back of houses is in most cases not possible. Certainly, thiswould make the costs considerably lower as it may even be possible toplough down channelling tubing/ducts for fibre cables but this ofteninvolves crossing gardens in the homes of people not wanting to connect.There is also the question of flowerbeds, bushes and trees, which can becostly to replace/restored. Finally, it would probably be an enormoustask to arrange permission from all the homeowners affected if thismethod should be employed.

A technique for installing fibre is described in document L.40 producedby the International Telecommunication Union (ITU-T Recommendation L.49,2003). Document L.40 describes a micro trench installation technique forfibre cables.

However, the present application describes a new method for producingmicro trenches and placing ducts/cables in the trenches which is calledMicro Trenching Technique (MTT). In this respect, there is a need in theart for a saw blade which may be used with the new method and/or whichimproves mentioned new method.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a saw blade which fullyor in part solves the problems of prior art solutions. More specificallyto a saw blade having a unique identity, and which identity can beread/identified under harsh environmental conditions which is the casewhen the saw blade is used for sawing micro trenches for ducts/cables(e.g. communication cables).

According to an aspect of the invention, above mentioned objects areachieved with a saw blade for a sawing machine, said sawing machinebeing arranged for cutting micro trenches by means of said saw blade,wherein said micro trenches are adapted for receiving at least oneduct/cable; wherein said saw blade comprises mechanical coding meansselected from the group consisting of holes, depressions and protrusionsarranged on said saw blade; and said holes, depressions and protrusionsbeing coding elements for forming at least one code symbol representinga unique identity for said saw blade.

According to another aspect of the invention, above mentioned objectsare achieved with a sawing machine arranged for cutting micro trenchesby means of at least one saw blade according to the invention, whereinsaid micro trenches are adapted for receiving at least one duct/cable;said sawing machine comprising second attachment means complementary tosaid first attachments means for attaching said at least one saw bladeto said sawing machine; further comprising reading means for readingsaid coding elements.

Different embodiments of the saw blade and the sawing machine above aredisclosed in the appended dependent claims.

Further, the invention also relates to a system comprising at least onesaw blade and at least one sawing machine according to the invention.

With a solution according to the present invention a saw blade and asawing machine are provided which allows identification of the uniqueidentity of the saw blade under harsh conditions which is the case whenmicro trenches are sawn. Thereby, such saw blades and sawing machinescan advantageously be used in micro trenching techniques described inthis disclosure and other relevant methods.

Other advantages and applications of the present invention will beapparent from the following detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended drawings are intended to clarify and explain the presentinvention, in which:

FIG. 1 shows a flow chart of MTT;

FIG. 2 shows a flow chart of an embodiment of MTT;

FIGS. 3a and 3b schematically shows a cross section of a roadway areawith a micro trench;

FIG. 4 schematically shows the cross section in FIG. 3, wherein themicro trench is filled with filling material such as sand and sealedwith two sealing layers;

FIG. 5 shows a typical layout of a FTTH network;

FIG. 6 shows how to saw branches to individual homes from a main microtrench;

FIG. 7 shows branching to individual homes if boring is used instead ofsawing;

FIG. 8 shows a sawing machine with its sawing blade/disc cutter and astabilizing device for placing ducts/cables immediately behind thesawing disc;

FIG. 9 shows the sawing machine where the stabilizing device is adaptedfor placing a plurality of ducts/cables at the same time whilemaintaining the order of the ducts/cables in the micro trench; and

FIG. 10 shows in detail where to cut the top duct so that it will belong enough to reach its final destination;

FIGS. 11-13 shows further embodiments of the stabilizing device (thechannels are only illustrated in FIGS. 11-13 and should therefore not beseen as true representations).

FIG. 14 shows a saw blade according to the present invention;

FIG. 15 illustrates mechanical coding elements according to theinvention;

FIG. 16 illustrates electro mechanical coding elements;

FIG. 17 shows the system for controlling the saw blade of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a saw blade for a sawing machine 10.The sawing machine 10 is of the type arranged for sawing/cutting microtrenches by means of the saw blade 1. To achieve the objects, the sawblade comprises mechanical coding means 2 selected from the groupconsisting of holes, depressions and protrusions which are arranged onthe saw blade 1. The holes, depressions and protrusions are codingelements for forming at least one code symbol 4 representing a uniqueidentity ID for the saw blade 1.

By giving the saw blade a unique identity the following advantages canbe added to the micro trenching process described in this disclosure,such as:

-   -   Full traceability of the saw blade from production to        destruction    -   Safer handling of the saw process by using the right blade    -   Optimization of the choice of saw blades relative to the        material in the ground for extending the lifetime of the saw        blade    -   Calculation of the saw blade optimum turning radius in relation        to the material in the ground for extending the life of the saw        blade    -   When the material in the ground changes, the program        automatically calculates the cost of replacing saw blades (e.g.        time multiplied by the hourly rate) this is compared to the        possibly increased wear and life expectancy of the saw blade    -   Quality assurance and process monitoring    -   Management of return system for saw blades    -   Automatic documentation of events and errors    -   Information from the sawing machine's data systems can be linked        to the saw blade    -   Immobilizer to prevent that invalid/incorrect saw blades to be        used    -   The collected history can be used directly in product        development    -   On-line billing based on wear and tear may be added when all the        data about what and how the saw blade has been used can be        obtained in real time or afterward    -   Specific properties for an individual saw blade (such as        coating, tolerances and guarantee conditions) can be        communicated to the machine's IT systems to prevent erroneous        and dangerous use    -   The position of the saw blade in X-, Y- and Z-coordinates are        documented in real time, this make it an exact spatial and        tabular description of the saw blades whole life

The mechanical coding means in the form of holes, depressions andprotrusions may have different depth or height or spatial location orsize according to an embodiment of the invention. Mentioned differencesare used for distinguishing different coding elements from each other,i.e. giving the holes, depressions and protrusions coding elementmeaning depending on mentioned depth, height, size and spatial location.For example, two depressions having different depth mean that theyrepresent two different coding elements. Hence, an almost infinite largenumber of characters may be constructed. Thereby, by combining thedifferent elements a large number of coding symbols may be formed.

FIG. 15 shows an example of different mechanical coding elements whichtogether form at least one coding symbol representing a unique identityID. The black circles represent holes, the white circles depressions andthe dashed circles protrusions, respectively in FIG. 15.

According to another embodiment of the invention present, the saw bladefurther comprises coding elements in the form of electro magnetic codingmeans 3 which may be combined with the mechanical coding elements forforming code symbols representing a unique identity ID for the sawblade. This embodiment is a safeguard against the harsh environmentalcondition in which the saw blades are used, i.e. the unique identity IDmay still be read even though dust and other debris from the microtrenching process covers the saw blade. The mechanical and electromagnetic coding means may also be more or less replicas of each otherthereby providing redundancy to the code reducing erroneous reading ofthe identity ID. Another alternative is to use Forward Error Correction(FEC) which is often used in tele and radio communications.

The electro magnetic coding means 3 are preferably comprised in a RFIDdevice, e.g. in the form of a chip or an electric circuit mounted on thesaw blade. FIG. 16 illustrates such as a RFID device comprising electromagnetic coding means 3.

It should however be realised that the coding elements may also comprisefurther information besides the unique identity. For example,manufacturer, production batch, type (so that correct type of saw bladeis mounted for a specific work), etc.

According to yet another embodiment of the invention, the code symbol 4further function as an immobilizer for the sawing machine 10 to whichthe saw blade is attached. For example, the on-board computer may beprogrammed to prevent the sawing machine from starting if the attachedsaw blade does not have a correct/valid identity.

As mentioned above, the saw blade is arranged to be used in a sawingmachine for sawing/cutting micro trenches. Thus, the saw blade comprisesfirst attachment means A1 for attaching said saw blade 1 to the sawingmachine 10. Hence, the sawing machine comprises second attachment meansA2 complementary to the first attachments means A1 for attaching the sawblade 1 to the sawing machine 10 when in use. Typically, an attachmentaxis (in this case second attachment means A2) arranged on the sawingmachine is inserted into a centre hole (in this case first attachmentmeans A1) arranged on the saw blade, thereafter a chuck is used tosecure the saw blade to the sawing machine.

It has been realised by the inventors that it is advantageous themechanical coding means 2 and the electro magnetic coding means 3 arearranged adjacent to the first attachment means A1 on the saw blade 1.The area on the saw blade adjacent to the first attachment means A1 isnot used for sawing in the ground which means that this particular areais protected from mechanical wear compared to the circumferential partof the saw blade and therefore suitable for the placement of the codingmeans. Therefore, according to this embodiment, the reading means on thesawing machine should in a corresponding manner be arranged adjacent tothe second attachment means A2.

FIG. 14 shows an embodiment of a saw blade according to the invention.This particular embodiment comprises both mechanical and electromagnetic coding elements. This makes it possible to identify the sawblade even if one of the methods (mechanical or electro magnetic) fails.

According to yet another embodiment of the invention the saw blade iscoated/covered with diamonds (not shown in FIG. 1), and is available inseveral different configurations dependent on ground and surfacematerial and desired cut depth and width. Currently the ratio width ismaximized to 40 mm and the depth of 600 mm. For fibre, 25 mm wide and400 mm deep is used in the normal case. Hence, the saw blade for sawingmicro trenches may be arranged for depths between 10 to 600 mm andwidths between 5 to 25 mm.

According to another embodiment the rotation of the saw blade is counterclockwise (up-cut) so that material is transported up in front of thesaw and can be collected in a container that is mounted in front of thesaw blade. The counter clockwise rotation of the saw blade also meansthat less debris is left in the micro trench.

The saw blade may further be cooled with water, and may be monitored bysensors that give indications of heat (sensor), wobbling (gyro), speed(tachometer), saw pressure (sensor) and wear (sensor). The wear of thesaw blade can be determined by analysing wave signals from the sound ofthe saw blade in operation.

Software that indicates and addresses emerging sensor deflection isinstalled in the machines on board computer (i.e. computer means). Heatand wobbling are the most common reasons for saw blade damage. The sawblade is stopped and lifted automatically at given parameters in orderto avoid a breakdown.

Further, the saw blade need be applied against the ground absolutelyvertically during the process to prevent wobbling and uneven wear. Agyro monitor so that this happens, the software in the on-board computerverify that the application is kept within given parameters, andterminates automatically upon failure.

Saw blade speed for best results should be smooth. Deviations from givenparameters are handled by the software in the on board computer.

Saw pressure is related to the solid nature of the ground material andthe speed at which the machine is driven forward. Sensors and controlsystems monitor the relationship between the saw blade pressure andspeed of the driving wheels and the software automatically controlrelations between these two.

With unique identity ID labelling, all the above information and anydeviation singled out geographically in X-, Y-, and Z-coordinates can belinked to each separate saw blade.

Methods for Labelling and Reading/Scanning Coding Elements

The labelling of saw blades can be done with a number of differentmethods depending on the surrounding environment, and how the productionline of the saw blades is designed. In order to ensure a lifetimelabelling which do not require major changes in the production line thefollowing methods for labelling and scanning may be used:

Labelling Coding Elements

Saw blades may be labelled mechanically by depressing techniques,punching or laser firing, with a number of subscript dots of differentdepth, height and size, and in different spatial relationships to eachother. The combination of deep, height, size and spatial distributiongives an infinite number of variables for forming code symbols. Thelabelling may preferably be carried out adjacent to the attachment ofthe blade, as part of the production of the saw blade. Each saw bladecan with this technique be given a unique identity.

Labelling is e.g. done with a tool that with a rotating punch generatesa unique point formation on each saw blade. The punch tool is associatedwith a software that post all the individual saw blades and adds theseattributes in written form on a packing slip that are applied to the sawblade on a sticker. Saw blade now has a unique identity that is passedto a database that is accessible from the saw machines on board computervia e.g. a Web interface.

Reading/Scanning Coding Elements and Identifying Code Symbol

The reading of a unique saw blade identity ID can be done with a numberof different suitable methods, such as:

-   -   1) Optically, using a laser scanner that is applied close to the        mounting of the saw blade on the sawing machine;    -   2) Mechanical machine attachment that uses a number of metal        pins read the depth and position of e.g. punched points which        means that the saw blade serves as a key in a “lock”; and    -   3) Electromagnetic reading using RFID technology if        electromagnetic coding means are arranged on the saw blade.

Methods 2 and 3 above in combination provide a very secure reading in atough environment. Formation (of e.g. sequences and positions of punchedholes in the saw blade) that makes up an unique identity ID can betranslated into characters that are read via the saw blades attachmentto the machine using electromagnetic reading means. Point data can beread by a number of spring attached metal balls that automaticallysenses point data on the blade. The balls positions varies depending onthe hole size and leaves imprint on a sensor plate. This translatesinformation into digital format that is read by the sawing machine's ITsystem. The combination of the above method enhances safety andreliability of decoding. Systems can however function individually butallows no conflicts between each other.

The sawing machine reads the saw blades unique identity ID which in thiscase acts as a key. Lock features can be added to the key depending onsecurity and guarantee reasons. The sawing machine can thus be providedwith immobilizer so that it can not start if the unique identity ID isincorrect. Information about a non-authorized saw blade usage may bedelivered (e.g. by means of wireless communication) to the machine'sowners, drivers and manufacturers if desired.

The information about the saw blade and its history is collected in thesawing machine's on board computer. The saw blade's identity ID islinked to other information that is generated by the sawing machine'svarious sensors which describe all deviations and conditions associatedwith use of the saw blade. This can for example be:

-   -   Runtime    -   Machine speed    -   Rotation speed    -   Wobbling    -   Temperatures    -   Ground conditions    -   Turn radius    -   Wear    -   Blade pressure    -   Etc.

All the above information is of importance for an optimal lifespan ofthe saw blade, and that the operation is carried out safely. Further,guarantees and other responsibilities will be easier to ensure.

After the saw blade has been used the saw blades remaining duration canbe calculated and a billing system based on real information is possibleto implement. The saw blade may be returned to the producer. A depositsystem based on real factors is created. A saw blade that has beenproperly used can be much easier to reuse and will be commanding asignificantly higher value than a wrongly used saw blade.

Hence, as understood from above, the invention also relates to a sawingmachine, and to a system comprising a saw blade and a sawing machine.

Sawing Machine

The sawing machine 10 according to the invention comprises secondattachment means A2 complementary to the first attachments means A1 forattaching the saw blade 1 securely to the sawing machine 10, when inuse. Further, the sawing machine 10 comprises reading means 20 forreading the coding elements arranged on the saw blade so as to identifythe unique identity of the saw blade. Preferably, the reading means 20are one or more in the group comprising: optical reading means, electromagnetic reading means, and mechanical reading means.

Furthermore, according to another embodiment of the invention, thepresent sawing machine 10 is arranged to not start if the uniqueidentity ID is incorrect, e.g. by including an immobilizer. If theidentity does not match, the sawing machine will not start and therebyoperation is impossible.

The sawing machine may also include one or more sensors 22 in the groupcomprising: heat sensors, gyro, speed sensors, pressure sensors, enginesensors and wear sensors; and computer means 23 in communication withthe reading means and sensors. The computer means 23 is arranged fordecoding and identifying the unique identity ID. The computer means 23may also be arranged for monitoring the sensors 22 and controlling theoperation of the sawing machine 10.

According to another embodiment, the sawing machine further compriseshigh precision GPS 24 in communication with the computer means 23 fordocumenting the use of the at least one saw blade 1 in X-, Y- andZ-coordinates as cartographic position data. Mentioned data may also betransmitted to a server unit by means of a second data flow, which meansthat the sawing machine may also comprises wireless communication meansfor communication with external communication device over one or morewireless communication systems, such as e.g. GSM, UMTS, WiFi, E-UTRA,etc.

System

Furthermore, the invention also relates to a system comprising at leastone saw blade 1 and at least one sawing machine 10 according to thepresent invention. Preferably, the system further comprises a serverunit 30 arranged for collecting and storing location and operation datafrom the high precision GPS 24, the sensors 22, and the computer means23.

The server unit 30 may further be arranged for analysing the locationand operation data and transmitting control data by means of first workorders in a first data flow to said computer means 23 after havinganalysed the above mentioned data. This control data can for exampletell the operator of the sawing machine to change to another type of sawblade, or to reduce driving speed depending on parameters in the GISserver analysis program. The GIS server analysis program parameterscontain factors, such as security factors, time factors, cost factors,etc.

Furthermore, mentioned analysed location and operation data may be usedby a back office master system for managing work orders, planningpurchase and service, and for statistical analyses and documentation ofthe micro trenching process. Therefore, the server unit 30 may also bearranged for acting as a hub between the sawing machine and an officeclient. The information stored in a first data base of the server unitis available and can be integrated to the business system's differentfunctions. Such as creating purchase orders and invoices.

Sawing Machine and Stabilizing Device

It has been realized by the inventors that the placement/installation ofducts/cables should preferably be made before the sides of the trenchcollapses and before stones (or debris) and in particular stones largerthan the width of the trench are wedged into the sides of the trench andprevents the installation of the ducts/cables all the way down to thebottom of the trench. By achieving this time (and money) can be savedsince the installation can be performed without unnecessaryinterruptions.

Therefore, a sawing machine as already mentioned is arranged for sawingmicro trenches in an area. In this respect, the machine comprises a sawblade, preferable circular in shape, for sawing/cutting the microtrenches. The produced micro trenches are adapted for receivingducts/cables which means that the micro trenches have the properdimensions.

The machine also comprises a stabilizing device arranged for stabilizingthe walls of the micro trench when placing ducts/cables, and for thispurpose the stabilizing device is positioned immediately behind the sawblade in the micro trench, so that the walls are stabilized until theducts/cables have bee placed/installed by means of guiding means whichare also arranged on the stabilizing device.

For stabilizing the walls of the trenches, the stabilizing devicecomprises suitable elements such as proper side elements which arearranged to “hold up” the walls until the ducts/cables have beeninstalled in the trenches. It is important that the stabilizing deviceis positioned immediately behind the saw blade so that the trenches sawnby the saw blade are stabilized directly after they are produced so thatthey do not collapse, or that debris or other dirt fall into thetrenches before the ducts/cables have been placed. Therefore, a closestdistance between the saw blade and the stabilizing device is larger than0 mm but less than 10 mm according to an embodiment. The dimension ofthe stabilizing device is dependent on the size of the ducts/cables, thenumber of ducts to be placed at the same time, and the depth forplacement in the trench. However, the width of the stabilizing deviceshould be slightly less then the width of the sawing blade.

Furthermore, for achieving controlled and automatic placement of theducts/cables the device has also guiding means which guides theducts/cables into the trench in a controlled and ordered manner. Thecombination of stabilization and guiding has proved to reduce cost andtime in an effective manner since the process of sawing and installingcan be performed at the same time. The guides are arranged on thestabilizing device and hence makes it possible to place the ducts/cablesinto the trench while the trench is stabilized by the device. Theducts/cables can therefore be placed with high precision into the trench(e.g. on the correct height in the trench) since the trench is “clean”as long as the trench is stabilized by the device.

The stabilizing device may be made of any suitable strong material sothat the trenches are stabilized. The material should preferably berigid, tough, hard and yet flexible so as to withstand stress duringoperation. The mounting of the stabilizing device to the sawing machineshould have an amount of flexibility to prevent damage if thestabilizing device is stuck in the trench. Steel or steel alloys aresuitable since they can be given the right properties by alloying withdifferent metals such as platinum and manganese. There is limited spacein the trench so the walls of the stabilizing device have to be thin aspossible so as to be able to accommodate the passing the ducts/cablesbut still have the properties mentioned above. Steel alloys in thehardness of about 400-700 Brinell have proved suitable for theseapplications. It has also been realised that the stabilizing device canbe made of moulded carbon fibre. Different parts of the stabilizingdevice can be cast separately and assembled into a stabilizing deviceassembly.

According to an embodiment, the device has an inlet and an outlet forducts/cables, the inlet and outlet being connected to the guiding means.Preferably, the guiding means are channels through which theducts/cables are guided through the stabilizing device. When inoperation, the inlet is preferably above ground and vertically or closeto vertically arranged while the outlet is below ground in the trenchand horizontally or close to horizontally arranged in order to minimizewear and tear on the ducts/cables. Therefore, a minimum distance betweenthe outlet and the saw blade (at ground lever) is slightly longer thanthe recommended minimum bending radius for the ducts/cables to beinstalled. This normally translates to somewhere between 100 to 500 mmmeasured at ground level, but other distances are possible. Further, theinlet, outlet and guiding means may together be removably attached onthe stabilizing device e.g. in the form of a removable cassette. Byhaving a removable cassette for the guiding means, the installation timeshortens in some cases as the time consuming task of inserting manyducts/cables into their respective channels may be avoided

It has also been realized by the inventors that an operating depth forthe stabilizing device in the micro trench should be up to 50 mm lessthan an operating depth for the saw blade according to an embodiment.This difference in depth between the saw blade and the stabilizingdevice, when in operation, decides how quickly the ground level maychange (i.e. goes down). The saw blade must have sawed the trench deepenough so that the stabilizing device never touches the bottom of thetrench in order to avoid the possibility of the stabilizing devicesticking to the ground. This avoids unnecessary forces on thestabilizing device and possible breakage. This may happen when theground level suddenly becomes lower.

Moreover, according to yet another embodiment, the stabilizing deviceand the saw blade are arranged to be elevated and lowered independentlyof each other. This is advantages when for example the saw blade has tobe changed due to wear or when another type of saw blade is needed (e.g.one type for asphalt and another type for concrete). Further, thestabilizing device may have to be replaced which may easily be performedif the two parts can be lowered and elevated independently of eachother. Also, during shorter interruptions in the sawing operation thesawing blade is elevated, but the stabilizing device must remain in theground, since the need for stabilization of the trench still exists.However, the stabilizing device and the saw blade may further bearranged to together be elevated and lowered, e.g. when undergroundinfrastructure is encountered both parts can be elevated so as to avoiddamage.

The stabilizing device is preferably mounted separately on the sawingmachine by means of a number of movable axes for elevation and lowering.The movable axes may be powered by a dedicated engine for this specificpurpose. Further, the sawing machine may have on its left and rightsides (in the sawing direction) quick mount attachments means anddriving means for both the stabilizing device and the saw blade.Thereby, any of the left or right sides of the sawing machine can beused for sawing and placing ducts/cables which may be necessary due tohindering infrastructure, traffic situation in the area, etc.

FIG. 9 shows an embodiment of a machine. The stabilizing device has afront part and a back part, wherein the front part is locatedimmediately behind the saw blade. It can also be seen that thestabilizing device has a section at the front part that has a shape thatis complementary to the shape of the saw blade which in this particularcase is circular. Thus, in case the section at the front part has aconcave circular shape with the same radius, or close to the sameradius, as the saw blade and is placed as close as possible and lessthan 10 mm away from the saw blade. The reason for this is that theunderground part of the stabilizing device must be arranged so close tothe saw blade such that it is virtually impossible for dirt, stones andother debris to fall to the bottom of the trench or wedge between thesides of the trench. The guiding means in this embodiment are guidingchannels inside the stabilizing device. The channels are illustratedwith dotted lines in the figures.

Further, the back part of the stabilizing device where the outlet isarranged may have different preferred shapes. One shape is substantiallyparallel to the complementary shape of the front section describedabove. Another shape is substantially opposite to the complementaryshape, and a third embodiment defines a shape for the back part which issubstantially diagonal from the base to the top of the back part in thebackwards direction. These embodiments are shown in FIGS. 11-13. It isfurther to be noted that the inlet, outlet and channels are arranged onthe back part of the stabilizing device in this embodiment. Thestabilizing device may also be axe shaped in cross section at frontpart.

Preferably, as mentioned above the stabilizing device has a maximumwidth in cross section that is equal to or slightly less than a widthfor the saw blade. The stabilizing device must be wide enough to haveroom for the ducts/cables to be installed, but small enough so that itcan be drawn along the sawed trench.

Another important aspect is that with the use of guiding means an orderof a plurality of ducts/cables is preserved when placed in the microtrench. This is very important when more than one duct is placed at thesame time. In one installation scenario, the duct/cable for a certainhouse is cut at a certain distance after the house. It is important thatthis duct/cable is one of the ducts/cables on top of the pile ofducts/cables in the trench, so that it can be easily found. Theduct/cable must be cut before the stabilizing device. Therefore it isimportant to know which one of all ducts/cables that enters thestabilizing device will come out on top in the trench. Moreover as thecolour of the duct/cable for a certain house is in many cases decidedbefore the sawing begins, the order of the ducts/cables must be arrangedso that the duct/cable with correct colour comes out on top, cut to thecorrect length, in the trench when that particular house is passed.

A method which allows the placement of a plurality of ducts/cables atthe same time has a very high commercial value since the process ofplacement can be performed much faster than what has previously beenknow in the art. Therefore, according to this embodiment, thestabilizing device has a plurality of guiding means each guiding one ora few ducts/cables into the trench. For example, the device may comprisea plurality of channels so arranged that a know order is preserved,which means that an order of the ducts/cables out of the stabilizingdevice is known form the order of ducts/cables into the stabilizingdevice, hence the order into and out of the stabilizing device isrelated and known. This can e.g. be achieved by a one-to-one mappingbetween the inlet and the outlet of the device. The order of theducts/cables should be arranged in such a way that one of theducts/cables on top of the pile of ducts/cables in the trench is alwaysthe one to be routed to the next location. Therefore, a downmostduct/cable entering the inlet will be an uppermost duct/cable out fromthe outlet, and the uppermost duct/cable entering the inlet will be adownmost duct/cable out from the outlet. The branching micro trenchesmay be sawn before the main trench as shown in FIGS. 6 and 7 or thebranching micro trenches may be sawn after the main trench is sawn. Theparticular order in which the trenches are sawn may be decided toachieve the best flow during the installation. Each branching microtrench goes to a final location for one of the ducts/cables from themain micro trench. When the main trench is sawn and the ducts/cables areinstalled, the uppermost duct/cable is cut (before it enters thestabilizing device) at a certain distance beyond the location of therespective branching trench, so that that duct/cable can be lifted androuted to the final location for that duct/cable, see FIG. 10. If thecut is made correctly the length of the duct/cable will be sufficient sothat the duct/cable is long enough to reach the final location withoutsplicing. In this way the ducts/cables are one by one routed to eachpassed location through the branches.

Depending on the width of the trench and the size of the ducts/cablesthere may be one or more ducts/cables side by side as the uppermostducts/cables in the main trench. It is important that the duct/cablenext to be routed to its final location is always one of the ones ontop. To achieve this is, when cutting the main trench and placing anumber of ducts/cables, to cut one of the uppermost ducts/cables, theone designated to this specific location, at a certain distance afterpassing the corresponding branching trench, so that the cut duct/cablecan be lifted and routed through that branching micro trench to itsfinal location. The duct/cable should be cut at a certain minimumdistance after passing the corresponding branching trench, so that, whenlifted from the main trench and routed towards its final location, thelength is sufficient to reach the final location without splicing.

If the stabilizing device (formerly known as “plough”) is designed withindividual channels for the ducts/cables or with individual channels,each with room for a few ducts/cables, it is easy to know whichduct/cable will be on top in the trench and thereby which duct/cableshould be cut before the stabilizing device. Example of such stabilizingdevice is shown in FIG. 9. The stabilizing device in this embodiment hasa duct/cable inlet and a duct/cable outlet which is connected to eachother by means of a plurality of channels as guiding means (illustratedwith dotted lines) for the ducts/cables. The underground outlet of thestabilizing device may in an embodiment comprise a “matrix” (or vector)part so arranged that the channels are arranged in a matrix with n rowand m columns, thereby in a controlled way horizontally and/orvertically separating the ducts/cables when placing them in the microtrench.

So in summary; one after the other, cutting one of the uppermostducts/cables, which one is designated to a certain location, at acertain minimum distance after each branch and thereafter lifting thisduct/cable from the main trench and routing it to its final locationthrough the branch.

The machine may further comprise at least one drum arranged for holdingthe ducts/communication cables before placing them into the micro trenchvia the stabilizing device. In this way easy access to the ducts/cablesis achieved.

Further, the machine may also comprises other suitable means, such as:one or more engine means for powering the saw blade and the stabilizingdevice and/or for driving means (e.g. drive train and wheels),communication means for wireless communication with e.g. a remote serverunit, processing means, memory means, sensors, GPS means, vehicle means,display means for displaying information such as graphics, data basemeans, reading means for reading mechanical coding means on the sawblade, immobilizer, etc.

Regarding the driving of the saw blade and/or the stabilizing devicethis can e.g. be performed by means of direct mechanical driving,hydraulic driving and electric driving. The mechanical driving gives thehighest power transmission ration while the electrical driving gives thelowest, so the former is preferred if high power is needed which oftenis the case.

Micro Trenching Technique (MTT)

In the following the MTT method is described so as to give a fullunderstanding if the present invention. FIG. 1 shows a flow chart of amethod for placing at least one duct/communication cable below a roadsurface in the area comprising the steps of:

-   -   cutting a micro trench in the area through the first layer L1        into the second layer L2;    -   placing at least one duct/communication cable in the micro        trench so that the at least one duct/cable is placed below the        first layer L1; and    -   filling the micro trench so as to restore the road surface.

FIGS. 3a and 3b schematically shows a cross section of an area in whicha duct is placed in a micro trench. The area in FIGS. 3a and 3b is athree dimensional region of a typical roadway area, wherein the areacomprises a first layer L1 being a road layer such as asphalt orconcrete, and a second layer L2 being a bearing layer for the firstlayer L1 and usually consisting of macadam, sand and earth. The secondlayer L2 is naturally located below the first layer L1 as shown in FIG.3.

The cutting step involves: cutting the micro trench through the firstlayer L1 into the second layer L2, which means that the micro trench iscut as shown in FIGS. 3a and 3b . The micro trench is cut so deep thatat least one duct/communication cable is placed in the micro trenchbelow the first layer L1 (i.e. all installed ducts/communication cablesare placed below the first layer L1). Using the present method all ductsand cables for fibre optic networks can be placed deep enough so thatthey are safe if the road layer L1 is removed and/or replaced, e.g. whenrepairing the road.

Thereafter, the at least one duct and/or a communication cable is placedin the micro trench. The duct is a duct arranged to hold “air-blownfibre” (so called EPFU) or fibre cables. The duct/s and/or thecommunication cable/s are placed in the micro trench so that they areentirely positioned below the first layer L1.

Finally, the micro trench is filled with a suitable filling material sothat the road surface is restored. The filling material is sand or anyother material with suitable properties. The micro trench is filled withthe filling material to a suitable level, and if needed the fillingmaterial is thereafter packed with a compactor that fits the width w ofthe micro trench.

Finally, the micro trench is sealed using a sealing material, such asbitumen, in order to get a water tight sealing. If a water tight sealingis not needed, patching may also be made with cold asphalt which is asimple and cheap method of restoration. A suitable amount of coldasphalt is simply poured and scraped into the micro trench, andthereafter compacted to a smooth and hard surface. Any excess asphaltcan then be collected and removed.

The filling step may according to a preferred embodiment involve thesteps of:

-   -   sealing the micro trench flush to a bottom of the first layer L1        with a first sealing S1; and    -   sealing the micro trench flush to a surface of the first layer        L1 with a second sealing S2.

FIG. 4 shows the above described embodiment. The surface and the bottomof the first layer L1 are indicated in FIG. 4. In order to obtain asealed repair with high adhesion it is recommended to pour hot bitumenor bitumen mix when sealing the micro trench. However, other materialsuch as concrete or polymer modified asphalt will work.

The first sealing S1 is put down to seal the micro trench substantiallyflush with the bottom of the first layer L1 so that the micro trench canbe cleaned with a high-pressure washer to remove any residue of sandfrom the asphalt/concrete edges. After washing, the micro trench may bedried and pre-heated using a propane burner and finally, the microtrench is filled flush with the top surface of the first layer L1 usinga suitable sealant such as a hot crack sealant based on bitumen.

According to yet another embodiment, the micro trench is cut with a disccutter/sawing machine having a diamond coated sawing disc. Such adiamond coated sawing disc can easily saw through even the hardestmaterials, such as stone and concrete, and has proved very useful in thepresent application since it provides exceptionally clean cuts whencutting micro trenches. Prior art methods to cut micro trenches, such asusing a sawing disc with tungsten carbide teeth, creates small cracks inthe edges of the micro trench that will make complete sealing afterwardsmuch harder and more expensive compared the present method.

The micro trench is preferably cut/sawed with a modified so-calledroad-saw (sawing machine) having a diamond coated sawing disc. Tofurther optimise the performance of the road saw in the presentapplication, the inventors have realised that one or more of thefollowing improvements are useful and should be considered asembodiments:

-   -   Change in rotational direction of the sawing disc to so-called        “up-cut” for improved transport of cuttings;    -   Modified cover for the sawing disc and a front outlet to        optimise the transport of cuttings and reduce spreading of dust        and leave the micro trench clean and ready for laying        ducts/cables;    -   Stabilizing device as shown in FIGS. 8 and 9 with one or more        guiding means for ducts/cables immediately after the sawing disc        so that micro trenching and placing of ducts/cables can be        carried out in one process. In case the stabilizing device has        guiding means for a plurality of ducts/cables, these guiding        means should be arranged so the outlets from the stabilizing        device are placed on top of each other in such a way that the        order of the ducts/cables from the inlet into the stabilizing        device and into the micro trench is preserved;    -   Trolley drawn by the road saw with holder for drums for        ducts/cables and warning tape with tracking wire; and    -   Servo to keep the sawing disc vertical on uneven surfaces, e.g.        when two wheels of the road-saw are on the pavement and two        wheels are on the road.

FIG. 8 shows an embodiment using a sawing machine comprising a sawingdisc arranged for up-cut. Up-cut is defined as the rotating direction ofthe sawing disc in relation to the sawing direction as shown by FIG. 8.All known sawing machines have the opposite rotating direction. Bychanging the rotating direction of the sawing machine to up-cut helps toremove the cut material from the micro trench, thereby providing “clean”micro trenches.

Further, the sawing machine comprises a stabilizing device arrangedimmediately behind the sawing disc, wherein the stabilizing device hasat least one guiding means, such as channels, for guiding the duct/cablewhen placed in the micro trench immediately after the sawing disc. If aplurality of ducts/cables is placed at the same time, the stabilizingdevice is arranged to be able to place the ducts/cables in preservedorder. This may be achieved by having individual channels for theducts/cables in the stabilizing device so that the order of theducts/cables will be maintained through the stabilizing device. Thereby,it is possible before the ducts/cables enter into the stabilizing deviceto identify which duct/cable will come out on top in the micro trenchand thereby making it possible to know which duct/cable to cut for eachfinal location, see FIG. 10.

Generally, the depth d of the micro trench should be larger than thedepth of the first layer d1 together with the height d2 of at least oneduct or at least one communication cable according to an embodiment,i.e. d>d1+d2 which means that the depth d of the micro trench is largerthan the height of the first layer d1 plus the combined height of oneore more ducts and/or communication cables. As can be deduced from FIGS.3a, 3b and 4, the above mentioned relation holds.

However, costs increase with increased depth d of the micro trench.Therefore, the micro trench should not be deeper than necessary. Normaldepth d of the micro trench can be around 400 mm, and unlike the width wof the micro trench, the depth d can often be adjusted continuouslywhile in operation when using a disc cutter. The cutter depth cantherefore be reduced gradually as the number of ducts laid in the microtrench is reduced.

Further, the micro trench should not be wider than necessary, since awider micro trench is more expensive than a narrow micro trench. On theother hand a narrower micro trench can make it more difficult to installthe ducts/cables, so there is an optimal width of the micro trench,since e.g. if the micro trench is too narrow, all ducts/cables will bepiled on top of each other so that the depth of the top duct/cable willbe too shallow.

From the above discussion, the inventors have through tests realisedthat suitable dimensions for a micro trench should have a depth dbetween 200-500 mm (and preferably 300-500 mm) and a width w between10-30 mm (and preferably 15-25 mm) according to an embodiment forinstallation efficiency and low cost. Further, with these dimensionsminimum disruption of traffic is possible when placing ducts/cablessince traffic can pass over an open micro trench.

Furthermore, with reference to the flow chart in FIG. 2, according toanother embodiment, the method for placing at least oneduct/communication cable comprises the steps of:

-   -   scanning an area by means of a ground penetrating radar; and    -   identifying obstacles in the area using data generated by the        ground generated radar,    -   cutting a micro trench in the area through the first layer L1        into the second layer L2;    -   placing at least one duct/communication cable in the micro        trench so that the at least one duct/communication cable is        placed below the first layer (L1); and    -   filling the micro trench so as to restore the road surface.

It should be noted that the steps of scanning and identifying areperformed before the other steps in the method according to thisembodiment.

According to this embodiment, the area is scanned by means of a groundpenetrating radar device, such as a GEO-radar or any other suitableequipment.

Thereafter, possible underground obstacles in the area, such as sewerpipes, electrical cables, construction structures, etc. are identifiedusing information generated by the ground penetrating radar device. Thescanning and identifying steps means that when performing the subsequentcutting step it may be avoided to accidentally cut/damage obstacles inthe area which may result in delay and extra cost in the micro trenchingprocess. After cutting a micro trench in the scanned area, at least oneduct and/or a communication cable is placed in the micro trench.Finally, the micro trench is filled with a suitable filling material sothat the road surface is restored.

The method may also involve the step of: installing or blowing fibre orfibre cable in one or more ducts if ducts were placed in the microtrench.

It should also be noted that the method described above also maycomprise the step of: making one or more branching points connected tothe micro trench. Preferably, the branching points may be made by meansof a diamond coated core drill or a hand-held sawing machine with adiamond coated sawing chain or disc. As for this described embodimentthe method may also comprise the further step of: boring one or morechannels from the branching points to one or more houses usingcontrolled or guided boring. It is important that channels are boredbelow the first layer L1 in the second bearing layer L2. Ducts/cablesare thereafter installed in these channels when the drill is pulledback.

Different aspects concerning the layout of micro trenches, branchingpoints and channels, and strategies of cutting, branching, etc, inrelation to and incorporated in the present method will be discussed inthe following description.

Layout

FIG. 5 shows a typical logical structure of a Fibre To The Home (FTTH)network in a residential area, where “D” is a distribution node and “F”is a splicing point where larger fibre cables are spliced to smallerones (or in case of a PON network where optical splitters are placed).The network between a distribution node D and a splicing point F iscalled distribution network and the network between the splicing point Fand the individual homes is called access network. Both the ducts/cablesfor the distribution network and for the access network can be installedusing the present method.

A residential area being constructed with FTTH is normally divided intoa number of smaller residential subareas. Somewhere in the residentialarea or outside of the residential area there must be a site whereoptical panels and electronics needed to form a so-called distributionnode D are housed. The distribution node D can be housed in an existingbuilding or in a small dedicated built building or in a large groundcabinet. Each distribution node D may contain electronics and opticalpanels for anywhere between a few hundred households up to severalthousand households. The size of the area to be built from a singledistribution node D can be adjusted within wide limits and dependsprimarily on practical considerations, such as space in the distributionnode D, difficulties with management of a large number of smallerdistribution nodes D, etc. This concept can also be adapted for anynumber of fibres per household.

There are two main types of FTTH networks: point-to-point-networks andpoint-to-multipoint networks. In a so-called point-to-point-network, thedistribution node D contains the other ends of all fibres that originatefrom the households in the residential area. If e.g. a residential areawith 500 households is being equipped with 2 fibres per house, therewill be 1000 incoming fibres to the distribution node D. Thedistribution node D should preferably have a central location in thearea being built as shown in FIG. 5.

The fibre structure of a point-to-multipoint-network or a so-calledPassive Optical Network (PON) is more or less the same. The differencebeing that the number of incoming fibres to the distribution node D inthis case equals the number of households divided by a factor (e.g. 8,16, 32, etc.). The examples in the continuing discussion are madeassuming that a point-to-point-network is being built. However,described methods also apply to a PON if only the distribution cablesare scaled accordingly.

Viewed from the distribution node D, distribution cables extend out tosplicing points F in manholes or cabinets. Distribution cables arenormally designed for the number of households in the area plus 10%spare so that in the future, newly built buildings easily can be addedto the network. In a point-to-point-network, if e.g. a splicing pointcovers an area with 22 houses and the requirement is two fibres perhouse, then 48 fibres from the distribution cable are needed. Fibresfrom the distribution cables are spliced in the splicing points F tofibres from the access cables. These access cables then extend to eachone of the houses being connected.

How many houses a splicing point F serves mainly depends on economicissues. If the covered area is too large, this will increase the averagelength of access cables to the houses, which increases costs. On theother hand, if the covered area is too small the cost for each housewill rise in relation to its share of splicing point F and distributioncable. Hence, there is an optimum size to the residential area where thecost is the lowest. The number of houses that would minimise the costdepends mainly on the topography of the residential area and how largethe plots of land are on which the houses are standing, but a rule ofthumb is that an optimum size is normally somewhere between 16 and 48houses from each splicing point F.

If micro trenching is carried out using a disc cutter according to anembodiment, the splicing point F should be placed centrally in eachresidential subarea, with e.g. around 22 houses. The splicing point Fcan be physically realised in a street cabinet or in a manhole by theroadside. Then, typically 10-12 ducts extend from the ground cabinet ormanhole each way along the road. Each of these ducts then extends intoeach of the houses. Finally, access cables are blown into each of theseducts.

Strategy when Cutting

Usually, residential areas have houses on both sides of a road, and thissituation can be tackled in one of two different ways: either microtrench in the roadside on both sides of the road and connect the housesto the closest micro trench, or micro trench on only one side of theroad or in the middle of the road and connect houses on both sides tothis micro trench.

However, to minimise the number of micro trenches across the road, startto micro trench to a boundary between two properties (houses) on theopposite side of the road according to an embodiment. Then place aduct/channelling tube in that micro trench to each one of the twoproperties. In this way, a micro trench across the road need only bemade for every second property on the opposite side of the road. Microtrenching across the road for every second property then this will be acheap and cost effective method.

Branching Off a Main Trench

Branching off from a main micro trench (a main micro trench is definedas a micro trench along a road) can be carried out in a number of ways.The branches may be sawn either before as shown in FIG. 6 or after themain trench is sawn. Both methods are best done at about a 45° anglefrom the main micro trench in order to obtain a large radius curve forthe ducts/tubing. The branches may cross the location of the main microtrench or go “flush” with the main trench. When the main micro trench issawed and the ducts/channelling tubes are laid it is easy to one by oneroute one of the uppermost tubes through each of the sawed branches upto each residence, as shown in FIG. 10 and to the right in FIG. 6.

An alternative method of branching is to first bore a hole at eachbranching point with a suitably sized core drill. The main micro trenchcan then be cut along all these holes in the same manner as describedabove as shown in FIG. 7. This method is suited both to making the houseconnections with a micro trench cut in the way described above as wellas making house connections with controlled boring.

An alternative method of branching is to first make a hole at eachbranching point. The holes may be made using a suitably sized core drill(for a round hole) or using a hand tool with a diamond cutting blade orchain (for a square hole). The main micro trench can then be cut alongall these holes in the same manner as described above and as shown inFIG. 7. This method is suited both to making the house connections witha micro trench cut in the way described above as well as making houseconnections with controlled boring. Controlled boring is sometimespreferred for making the house connections, because it avoids (e.g. goesunder) obstacles like fences, hedges, trees, etc. However, another pieceof expensive machinery (core drill) is needed at the installation site.

Finally, it should be understood that the present invention is notlimited to the embodiments described above, but also relates to andincorporates all embodiments within the scope of the appendedindependent claims.

The invention claimed is:
 1. Sawing machine for sawing micro trenches inan area comprising a first layer and a second layer, said first layerbeing a surface layer comprising asphalt or concrete, and said secondlayer being a bearing layer to said first layer, wherein said microtrenches are adapted for receiving at least one duct/cable; said sawingmachine comprising a stabilizing device arranged for stabilizing thewalls of the micro trenches when placing ducts/cables into the microtrenches, and further comprising at least one saw blade comprisingcoding elements forming at least one code symbol representing a uniqueidentity for said saw blade, wherein said at least one code symbolfunction as an immobilizer for said sawing machine, said sawing machinebeing arranged to not start if said unique identity is not valid. 2.Sawing machine according to claim 1, wherein said coding elementscomprise electromagnetic coding means.
 3. Sawing machine according toclaim 2, wherein said electromagnetic coding means are comprised in aRFID device.
 4. Sawing machine according to claim 1, further comprisingfirst attachment means for attaching said saw blade to said sawingmachine.
 5. Sawing machine according to claim 4, wherein said codingelements comprise mechanical coding means and electromagnetic codingmeans, and said mechanical coding means and said electromagnetic codingmeans are arranged adjacent to said first attachment means.
 6. Sawingmachine according to claim 1, wherein said saw blade is diamond coatedand is arranged for up-cut.
 7. Sawing machine according to claim 1,wherein said saw blade is arranged for sawing micro trenches having adepth between 10 to 600 mm and a width between 5 to 25 mm.
 8. Sawingmachine according to claim 1, further comprising reading means forreading said coding elements.
 9. Sawing machine according to claim 8,wherein said reading means are one or more in the group comprising:optical reading means, electromagnetic reading means, and mechanicalreading means.
 10. Sawing machine according to claim 9, furthercomprising one or more sensors in the group comprising: heat sensors,gyro, speed sensors, pressure sensors, engine sensors, and wear sensors.11. Sawing machine according to claim 10, further comprising computermeans in communication with said reading means and sensors, saidcomputer means being arranged for decoding and identifying said uniqueidentity.
 12. Sawing machine according to claim 11, further comprisinghigh precision GPS in communication with said computer means fordocumenting the use of said at least one saw blade in X-, Y- andZ-coordinates.
 13. Sawing machine according to claim 12, wherein saidcomputer means further is arranged for monitoring said sensors andcontrolling the operation of said sawing machine.
 14. Sawing machineaccording to claim 13, further comprising wireless communication meansfor communication with external communication device over wirelesscommunication systems.
 15. A system for cutting micro trenchescomprising at least one sawing machine according to claim 14 and furthercomprising a server unit comprising communication means and a firstdatabase, and being arranged for collecting and storing position andoperation data from said high precision GPS, said sensors, and saidcomputer means by means of a second data flow.
 16. System according toclaim 15, wherein said server unit further is arranged for analyzingsaid position and operation data and transmitting control data to saidcomputer means by means of a first data flow comprising first workorders containing said control data.
 17. System according to claim 15,wherein said server unit further is arranged for acting as a hub betweensaid sawing machine and an office client.
 18. Sawing machine accordingto claim 1, wherein said coding elements are in the form of mechanicalcoding means selected from the group consisting of holes, depressionsand protrusions arranged on said saw blade.